Synonym: Entamoeba debliecki, pro parte.
This non-pathogenic species was first described from the intestines of sheep in Sumatra, but it is common thruout the world. Noble and Noble (1952) found it in the feces of all of 25 sheep from California and Washington. Triffitt (1926) reported it from the feces of the sable antelope (Hippotragus niger) and common waterbuck (Cobus ellipsiprymus) in Africa.
By a historical accident, the name of the pig entamoeba rather than that of the sheep entamoeba has been used for the entamoeba of the goat. Nieschulz (1923) gave the first description of E. debliecki (a synonym of E. suis) from the pig and soon after (1923a) found what appeared to be the same species in the large intestine of the goat in Holland. Hoare (1940) found it in the feces of 10 out of 14 goats in England and redescribed it under the name E. debliecki. Noble and Noble (1952) found it in the feces of 27 out of 28 goats in the United States and called it E. polecki (the name they used for the pig entamoeba). However, they considered the uninucleate entamoebae of cattle, goats, pigs and sheep to be morphologically indistinguishable. Since goats share a great many parasites with sheep but relatively few with swine, and in the absence of crossinfection experiments to the contrary, the best name for the goat entamoeba is E. ovis.
The trophozoites of E. ovis measure 11 to 12 by 13 to 14 u. The nucleus typically contains a large, pale endosome generally composed of several granules, a ring of peripheral chromatin, and numerous small granules between the endosome and the nuclear membrane. In some cases there is very little peripheral chromatin and in others the endosome may be very small. The cysts are 4 to 13 u in diameter with a mean of 7 u and contain a single nucleus when mature. They usually contain numerous chromatoid bodies of varying size, shape and abundance and a glycogen vacuole.
The cysts of the form from the goat are 4 to 13 u in diameter. Hoare (1940) found 2 races which differed in size. The cysts of one ranged from 5 to 9 u in diameter with a mode of 6.7 u, while the cysts of the other ranged from 9 to 13 u with a mode of 10.4 u Noble and Noble (1952), however, found only a single race with cysts ranging in diameter from 4 to 12 u with a mean of 6.4 u.
It is quite likely that E. ovis is a synonym of E. bovis, but until cross infection experiments have been carried out, it is thought best to retain it as a separate species.
Noble (1954) found this species in the feces of all of 12 goats he examined on Luzon in the Philippines. He saw only 2 trophozoites. They were 12 u across, had broad, rounded pseudopods whose ends had fairly clear ectoplasm, and food vacuoles containing bacteria. The cysts are 5 to 16 u in diameter with a mean of 9.7 u, and contain a single nucleus. The endosome is usually a small, central dot but may be eccentric. Peripheral chromatin is often absent or may appear as a few large, irregular granules. The entire nucleus is filled with fine granules which may form a ring around the endosome. The cyst contains 1 or more large glycogen vacuoles and from one to a large number of chromatoid bodies varying in shape from small, irregular masses to a single, large, sausage-shaped body. Noble considered this species to differ from the Entamoeba in American goats in that the peripheral chromatin rarely forms a heavy ring, the endosome is usually a single, small dot, and a periendosomal ring of chromatin is usually present.